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HI folks! As some of you may know, one of the dreams of our friend Patrick Davis (aka. P@T, Enjoybiking) was the idea of designing a mic that could have the "tube" sound, but that could also be very cheap to build. We discussed the topic many times, and the idea of having a solid state tube emulation was a really fascinating option that was always on the table. Some time ago I found a paper from Dimitri Danyuk called "Triode Emulator", and in this paper he proposes very a simple way to "emulate" triode behavior using a JFET with very specific values for drain and source resistors. Later, I found this page: Which provides a way to calculate (look at the end of the page) the required drain and source resistor values using some JFET parameters like:
And also the input voltage of the circuit (VCC). So, I decided to try a design using the Dimitri Danyuk approach, with the values calculated from the Fetzer Valve page. You could find the schematic here: /g/MicBuilders/files/Homero%20Leal%27s%20Files/Pat%27s%20Mic/Pat%27s%20Mic.pngCircuit design uses a Charge Amplifier input stage, a JFET middle stage (providing the "valve" tone"), and finally a impedance balanced output stage with a Sallen Key HPF at about 19.XHz. Also, a custom voltage regulator is used, using a BC549C NPN and a zener, very similar to the one used on some very known chinese mics. This VR provides about 9.4V for VCC. I used two drain resistors and two source resistors, so it could be easier to approach the right values calculated by the Fetzer Valve page, by using the combination of two resistors. As the JFET stage may have an amplification level on the signal, I also used two capacitors for the charge amplifier, this way you could reduce output level by placing an additional capacitor (some math required). I know the design may have some room for improvement, but I can confirm I have working mic with this design, and it seems to my untrained ear, that it has a very sleek and warm sound, very similar to the sound of the valve mics. For the build, I used a cheap Zramo donor mic from Amazon, which that very nice 26mm electret capsule we have talked about before. I decided to name this schematic? " Pat's Mic"... in memory of our friend and former member of this group, P@T?(Patrick Davis, R.I.P.) This post is for your review and consideration, and please if you have any ideas for improvement, don't hesitate to let me know. Thank you, and kind regards! HL
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Hey?Homero, what a lovely way to remember P@T and a great idea too. I have only ever used the fetzervalve (FETs or Valve) as a guitar pedal and never would have dreamed of using it in a mic! Any change of you creating PCBs of this?
Kind regards, Germar Tischler
HI folks!
As some of you may know, one of the dreams of our friend Patrick Davis (aka. P@T, Enjoybiking) was the idea of designing a mic that could have the "tube" sound, but that could also be very cheap to build.
We discussed the topic many times, and the idea of having a solid state tube emulation was a really fascinating option that was always on the table.
Some time ago I found a paper from Dimitri Danyuk called "Triode Emulator", and in this paper he proposes very a simple way to "emulate" triode behavior using a JFET with very specific values for drain and source resistors.
Later, I found this page:
Which provides a way to calculate (look at the end of the page) the required drain and source resistor values using some JFET parameters like:
And also the input voltage of the circuit (VCC).
So, I decided to try a design using the Dimitri Danyuk approach, with the values calculated from the Fetzer Valve page.
You could find the schematic here:
/g/MicBuilders/files/Homero%20Leal%27s%20Files/Pat%27s%20Mic/Pat%27s%20Mic.png
Circuit design uses a Charge Amplifier input stage, a JFET middle stage (providing the "valve" tone"), and finally a impedance balanced output stage with a Sallen Key HPF at about 19.XHz.
Also, a custom voltage regulator is used, using a BC549C NPN and a zener, very similar to the one used on some very known chinese mics. This VR provides about 9.4V for VCC.
I used two drain resistors and two source resistors, so it could be easier to approach the right values calculated by the Fetzer Valve page, by using the combination of two resistors.
As the JFET stage may have an amplification level on the signal, I also used two capacitors for the charge amplifier, this way you could reduce output level by placing an additional capacitor (some math required).
I know the design may have some room for improvement, but I can confirm I have working mic with this design, and it seems to my untrained ear, that it has a very sleek and warm sound, very similar to the sound of the valve mics.
For the build, I used a cheap Zramo donor mic from Amazon, which that very nice 26mm electret capsule we have talked about before.
I decided to name this schematic? "Pat's Mic"... in memory of our friend and former member of this group, P@T?(Patrick Davis, R.I.P.)
This post is for your review and consideration, and please if you have any ideas for improvement, don't hesitate to let me know.
Thank you, and kind regards!
HL
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Thank you Germar! The final version of the PCB will be available?as a PCBWay Shared Project. Just would like to have any feedback from the group before it goes final.
Regards!
HL
Hey?Homero, what a lovely way to remember P@T and a great idea too. I have only ever used the fetzervalve (FETs or Valve) as a guitar pedal and never would have dreamed of using it in a mic! Any change of you creating PCBs of this?
Kind regards, Germar Tischler
HI folks!
As some of you may know, one of the dreams of our friend Patrick Davis (aka. P@T, Enjoybiking) was the idea of designing a mic that could have the "tube" sound, but that could also be very cheap to build.
We discussed the topic many times, and the idea of having a solid state tube emulation was a really fascinating option that was always on the table.
Some time ago I found a paper from Dimitri Danyuk called "Triode Emulator", and in this paper he proposes very a simple way to "emulate" triode behavior using a JFET with very specific values for drain and source resistors.
Later, I found this page:
Which provides a way to calculate (look at the end of the page) the required drain and source resistor values using some JFET parameters like:
And also the input voltage of the circuit (VCC).
So, I decided to try a design using the Dimitri Danyuk approach, with the values calculated from the Fetzer Valve page.
You could find the schematic here:
/g/MicBuilders/files/Homero%20Leal%27s%20Files/Pat%27s%20Mic/Pat%27s%20Mic.png
Circuit design uses a Charge Amplifier input stage, a JFET middle stage (providing the "valve" tone"), and finally a impedance balanced output stage with a Sallen Key HPF at about 19.XHz.
Also, a custom voltage regulator is used, using a BC549C NPN and a zener, very similar to the one used on some very known chinese mics. This VR provides about 9.4V for VCC.
I used two drain resistors and two source resistors, so it could be easier to approach the right values calculated by the Fetzer Valve page, by using the combination of two resistors.
As the JFET stage may have an amplification level on the signal, I also used two capacitors for the charge amplifier, this way you could reduce output level by placing an additional capacitor (some math required).
I know the design may have some room for improvement, but I can confirm I have working mic with this design, and it seems to my untrained ear, that it has a very sleek and warm sound, very similar to the sound of the valve mics.
For the build, I used a cheap Zramo donor mic from Amazon, which that very nice 26mm electret capsule we have talked about before.
I decided to name this schematic? "Pat's Mic"... in memory of our friend and former member of this group, P@T?(Patrick Davis, R.I.P.)
This post is for your review and consideration, and please if you have any ideas for improvement, don't hesitate to let me know.
Thank you, and kind regards!
HL
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I love this “Fetzervalve” idea and would certainly build a couple - I regret that I’m not very technical and have no “feedback” to offer but I so appreciate this group (even though I mostly lurk in the shadows!)
I want to express support and encouragement to you, Homero, in pursuing this - if it means anything I’ll gladly be in line to obtain a couple PCBs early on
Cheers, Phil
Thank you Germar! The final version of the PCB will be available?as a PCBWay Shared Project. Just would like to have any feedback from the group before it goes final.
Regards!
HL
Hey?Homero, what a lovely way to remember P@T and a great idea too. I have only ever used the fetzervalve (FETs or Valve) as a guitar pedal and never would have dreamed of using it in a mic! Any change of you creating PCBs of this?
Kind regards, Germar Tischler
HI folks!
As some of you may know, one of the dreams of our friend Patrick Davis (aka. P@T, Enjoybiking) was the idea of designing a mic that could have the "tube" sound, but that could also be very cheap to build.
We discussed the topic many times, and the idea of having a solid state tube emulation was a really fascinating option that was always on the table.
Some time ago I found a paper from Dimitri Danyuk called "Triode Emulator", and in this paper he proposes very a simple way to "emulate" triode behavior using a JFET with very specific values for drain and source resistors.
Later, I found this page:
Which provides a way to calculate (look at the end of the page) the required drain and source resistor values using some JFET parameters like:
And also the input voltage of the circuit (VCC).
So, I decided to try a design using the Dimitri Danyuk approach, with the values calculated from the Fetzer Valve page.
You could find the schematic here:
/g/MicBuilders/files/Homero%20Leal%27s%20Files/Pat%27s%20Mic/Pat%27s%20Mic.png
Circuit design uses a Charge Amplifier input stage, a JFET middle stage (providing the "valve" tone"), and finally a impedance balanced output stage with a Sallen Key HPF at about 19.XHz.
Also, a custom voltage regulator is used, using a BC549C NPN and a zener, very similar to the one used on some very known chinese mics. This VR provides about 9.4V for VCC.
I used two drain resistors and two source resistors, so it could be easier to approach the right values calculated by the Fetzer Valve page, by using the combination of two resistors.
As the JFET stage may have an amplification level on the signal, I also used two capacitors for the charge amplifier, this way you could reduce output level by placing an additional capacitor (some math required).
I know the design may have some room for improvement, but I can confirm I have working mic with this design, and it seems to my untrained ear, that it has a very sleek and warm sound, very similar to the sound of the valve mics.
For the build, I used a cheap Zramo donor mic from Amazon, which that very nice 26mm electret capsule we have talked about before.
I decided to name this schematic? "Pat's Mic"... in memory of our friend and former member of this group, P@T?(Patrick Davis, R.I.P.)
This post is for your review and consideration, and please if you have any ideas for improvement, don't hesitate to let me know.
Thank you, and kind regards!
HL
-- Phil Manning ~ classic recording studio
~piano tuning & serviceAjax studio: 905.231.3189
Pickering shop/office: 416.907.3562
cell: 905.626.3727
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Homero,
That's a really cool project and a nice tribute to Pat.?
Would love to hear a comparison to a regular mic.
Thanks,
-Scott
On 4/12/22 20:22, Homero Leal wrote:
HI folks!
As some of you may know, one of the dreams of our friend Patrick
Davis (aka. P@T,
Enjoybiking) was the idea of designing a mic that could have the
"tube" sound, but that could also be very cheap to build.
We discussed the topic many times, and the idea of having a solid
state tube emulation was a really fascinating option that was
always on the table.
Some time ago I found a paper from Dimitri Danyuk called "Triode
Emulator", and in this paper he proposes very a simple way to
"emulate" triode behavior using a JFET with very specific values
for drain and source resistors.
Later, I found this page:
Which provides a way to calculate (look at the end of the page)
the required drain and source resistor values using some JFET
parameters like:
And also the input voltage of the circuit (VCC).
So, I decided to try a design using the Dimitri Danyuk approach,
with the values calculated from the Fetzer Valve page.
You could find the schematic here:
/g/MicBuilders/files/Homero%20Leal%27s%20Files/Pat%27s%20Mic/Pat%27s%20Mic.png
Circuit design uses a Charge Amplifier input stage, a JFET middle
stage (providing the "valve" tone"), and finally a impedance
balanced output stage with a Sallen Key HPF at about 19.XHz.
Also, a custom voltage regulator is used, using a BC549C NPN and a
zener, very similar to the one used on some very known chinese
mics. This VR provides about 9.4V for VCC.
I used two drain resistors and two source resistors, so it could
be easier to approach the right values calculated by the Fetzer
Valve page, by using the combination of two resistors.
As the JFET stage may have an amplification level on the signal, I
also used two capacitors for the charge amplifier, this way you
could reduce output level by placing an additional capacitor (some
math required).
I know the design may have some room for improvement, but I can
confirm I have working mic with this design, and it seems to my
untrained ear, that it has a very sleek and warm sound, very
similar to the sound of the valve mics.
For the build, I used a cheap Zramo donor mic from Amazon, which
that very nice 26mm electret capsule we have talked about before.
I decided to name this schematic? "Pat's Mic"...
in memory of our friend and former member of this group, P@T?(Patrick
Davis, R.I.P.)
This post is for your review and consideration, and please if you
have any ideas for improvement, don't hesitate to let me know.
Thank you, and kind regards!
HL
--
---- Scott Helmke ---- scott@... ---- (734) 604-9340 ----
"I have ceased distinguishing between the religious and the secular,
for everything is holy" - Joe Henry
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Why do you need RD1 and RD2, wouldn't be one RD enough? Same for RS.
Would we need a HexInverter or something else for the polarisation Voltage?
With the OPA and the Fet and T1 could there be a problem with the current from the Phantompower?
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Any recording tests you could share?
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Why do you need RD1 and RD2, wouldn't be one RD enough? Same for RS.Resistor?values for RD and RS need to be very specific, depending on IDSS, VP JFET values, and input voltage. Two resistors are used to make it easy to match the required values. Look at the ?page a the bottom, for the calculator.
Would we need a HexInverter or something else for the polarisation Voltage?
Yes, if you want to use a LDC capsule.
With the OPA and the Fet and T1 could there be a problem with the current from the Phantompower?
Yes, if the JFET IDSS value is to high. OPA1642 uses about 3.6mA. So, it is recommended to use a JFET with a low IDSS. The one I used has a 2.1mA IDSS value.
Regards!
HL
El jue, 14 abr 2022 a la(s) 02:16, Mic Scharf ( micscharf@...) escribió: Why do you need RD1 and RD2, wouldn't be one RD enough? Same for RS.
Would we need a HexInverter or something else for the polarisation Voltage?
With the OPA and the Fet and T1 could there be a problem with the current from the Phantompower?
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Thank you Jules, Phil and Scott!
Just waiting?to receive latest?PCB revision. Will try to upload some recording tests over the next few days.
If somebody wants to do some more "formal" tests on this design, please send me an email and let me know . I don't have the best conditions/equipment to do it?@home.
El mié, 13 abr 2022 a la(s) 20:08, Scott Helmke ( scott@...) escribió:
Homero,
That's a really cool project and a nice tribute to Pat.?
Would love to hear a comparison to a regular mic.
Thanks,
-Scott
On 4/12/22 20:22, Homero Leal wrote:
HI folks!
As some of you may know, one of the dreams of our friend Patrick
Davis (aka. P@T,
Enjoybiking) was the idea of designing a mic that could have the
"tube" sound, but that could also be very cheap to build.
We discussed the topic many times, and the idea of having a solid
state tube emulation was a really fascinating option that was
always on the table.
Some time ago I found a paper from Dimitri Danyuk called "Triode
Emulator", and in this paper he proposes very a simple way to
"emulate" triode behavior using a JFET with very specific values
for drain and source resistors.
Later, I found this page:
Which provides a way to calculate (look at the end of the page)
the required drain and source resistor values using some JFET
parameters like:
And also the input voltage of the circuit (VCC).
So, I decided to try a design using the Dimitri Danyuk approach,
with the values calculated from the Fetzer Valve page.
You could find the schematic here:
/g/MicBuilders/files/Homero%20Leal%27s%20Files/Pat%27s%20Mic/Pat%27s%20Mic.png
Circuit design uses a Charge Amplifier input stage, a JFET middle
stage (providing the "valve" tone"), and finally a impedance
balanced output stage with a Sallen Key HPF at about 19.XHz.
Also, a custom voltage regulator is used, using a BC549C NPN and a
zener, very similar to the one used on some very known chinese
mics. This VR provides about 9.4V for VCC.
I used two drain resistors and two source resistors, so it could
be easier to approach the right values calculated by the Fetzer
Valve page, by using the combination of two resistors.
As the JFET stage may have an amplification level on the signal, I
also used two capacitors for the charge amplifier, this way you
could reduce output level by placing an additional capacitor (some
math required).
I know the design may have some room for improvement, but I can
confirm I have working mic with this design, and it seems to my
untrained ear, that it has a very sleek and warm sound, very
similar to the sound of the valve mics.
For the build, I used a cheap Zramo donor mic from Amazon, which
that very nice 26mm electret capsule we have talked about before.
I decided to name this schematic? "Pat's Mic"...
in memory of our friend and former member of this group, P@T?(Patrick
Davis, R.I.P.)
This post is for your review and consideration, and please if you
have any ideas for improvement, don't hesitate to let me know.
Thank you, and kind regards!
HL
--
---- Scott Helmke ---- scott@... ---- (734) 604-9340 ----
"I have ceased distinguishing between the religious and the secular,
for everything is holy" - Joe Henry
|
I know I haven't really posted before but I am so sorry to hear that P@T?passed.... I didn't know until now.? I really appreciated his insights.? He's been a good teacher and I will miss his wisdom. Homero, thank you for doing this.? I think it's an amazing way to honor your friend.? I would love to build this mic when you finalize the design.? I have been looking at a design similar to this one with the idea of having a Charge Amp with an Opa.? Henry at Audioimprov gave me some really great leads for some schematics from this site but I'm not sure where my notes are.? The main difference seemed to be that the JFET was BEFORE the Opa.? Thanks everyone for all of you passion and heart you put into our hobby.? :)
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Scott Wurcer used to be a member here and he did a thorough study of using a charge amp in a mic. As I recall it was very impressive, and probably about 6 or 7 years ago. The designs might still be in the files etc if you look for Scott’s work. It was also written up in Linear Audio here? and here?
There is also good information here?
toggle quoted message
Show quoted text
I know I haven't really posted before but I am so sorry to hear that P@T?passed.... I didn't know until now.? I really appreciated his insights.? He's been a good teacher and I will miss his wisdom. Homero, thank you for doing this.? I think it's an amazing way to honor your friend.? I would love to build this mic when you finalize the design.? I have been looking at a design similar to this one with the idea of having a Charge Amp with an Opa.? Henry at Audioimprov gave me some really great leads for some schematics from this site but I'm not sure where my notes are.? The main difference seemed to be that the JFET was BEFORE the Opa.? Thanks everyone for all of you passion and heart you put into our hobby.? :)
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Hello Homero,
I hope all is well.? Has there been any further developments on this circuit, and have you had a chance to run any tests???
I am rather new with some of these concepts.? Could the JFET and/or the transistor be replaced by using a Quad JFET Opa?? An example would be the?OPA1644 (quad).? Not sure if there are?triple Op Amps but could that be something too?? I like minimizing parts when I can.
On Friday, April 29, 2022, 06:25:18 AM PDT, goldenhours_71 <davidstalling@...> wrote:
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Hi all,
?
Here's a quick update on the test build with the latest?PCB.
?
I'm experiencing a weird low frequency noise below 1khz. It's?not too high, but can be perceived. At first I thought?it was only room noise, but the?noise remains if I replace the capsule with a small ceramic capacitor. So, it's definitely?something?on the circuit.
?
I have been doing some tests trying to isolate the problem.??At first, I thought it was caused by the current regulator, but it seems to be caused by the JFET, or a combination of JFET and VR.?
?
If I remove the JFET and leave only both OPAs, the noise is gone (VR in place).
?
Also, if I replace the VR for a single 2k resistor, the noise is gone.?
HL
?
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May I suggest you decrease significantly C8. In combination with
R15, its -3dB cut-off is at 0.015 Hz.
! Would think 100nF is largely enough there. It may not be the
answer to your problem, though, just speculating.
Le 06/05/2022 à 05:11, Homero Leal a
écrit?:
toggle quoted message
Show quoted text
Hi all,
?
Here's a
quick update on the test build with the latest?PCB.
?
I'm
experiencing a weird low frequency noise below 1khz. It's?not
too high, but can be perceived. At first I thought?it was only
room noise, but the?noise remains if I replace the capsule
with a small ceramic capacitor. So, it's
definitely?something?on the circuit.
?
I have been
doing some tests trying to isolate the problem.??At first, I thought
it was caused by the current regulator, but it seems to be
caused by the JFET, or a combination of JFET and VR.?
?
If I remove
the JFET and leave only both OPAs, the noise is gone (VR in
place).
?
Also, if I
replace the VR for a single 2k resistor, the noise is gone.?
HL
?
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Le 05/05/2022 à 19:27, TheCanDo via
groups.io a écrit?:
Could
the JFET and/or the transistor be replaced by using a Quad JFET
Opa?? An example would be the?OPA1644 (quad).
In terms of functionalities, it would certainly work.
However, the subject here is getting the circuit to sound like a
vacuum tube. An opamp could not do that.
? Not sure if there are?triple
Op Amps but could that be something too?
No. only singles, duals and quads.
However a combination of a dual with a single? or three singles
could be functional.
A quad would probably exceed the available current.
I like minimizing
parts when I can.
(Almost) Everybody does.
But minimalism is not a proper design endeavour. It takes what it
takes to make the thing work.
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An additional RC filter would work, or simply adding a resistor between the BC549 and C14, and increasing C14 to push the RC time constant below audibility. The op-amps have good power supply noise rejection, but the FET has none. It needs pure DC.
The advantage of the zener plus transistor style VR in China mics is operation at low voltage, like 3V PIP for use with PC sound cards. The disadvantage is it's noisy.
|
Thank you Jerry Lee and Henry,
@Jerry Lee Marcel?I reduced the value of C8 to 1uf. Also there was an error on the C15 value, it should be 1000p instead of 0.1uf.
@William Spragens?The additional RC filter after VR was added to a new PCB design and sent to PCBWay. Thank you!
Here is version 1.1:
Also a quick update, replacing 10V zener with two 5.1V zeners in series, seems to fix the problem with the LF noise, but VCC is reduced from 9.4V to 8.5V aprox. This should not be a problem, since AFAIK...? JFET drain voltage is not critical to get it working in triode mode.
Waiting for the new PCB version with the additional RC filter. Will let you know how it?goes in a?few days.
Kind regards!
HL
An additional RC filter would work, or simply adding a resistor between the BC549 and C14, and increasing C14 to push the RC time constant below audibility. The op-amps have good power supply noise rejection, but the FET has none. It needs pure DC.
The advantage of the zener plus transistor style VR in China mics is operation at low voltage, like 3V PIP for use with PC sound cards. The disadvantage is it's noisy.
|
Homero - Thank you for the updates!?? 1. Is the charge amp being accomplished through the Op Amps???
2. Is it possible to use a Jfet with a built in diode for the triode section?? Maybe something like the K596 Jfet?
Jerry - Thank you for the input.? My train of thought was that a Jfet Op Amps may be used to replace the discrete Jfet in the triode mode.? My understanding is that Jfet Op Amps essentially have multiple Jfets?structures on one IC.? Is it not possible to use them in this way?? ?
Thanks in advance!??
On Friday, May 6, 2022, 08:50:19 AM PDT, Homero Leal <homero.leal@...> wrote:
Thank you Jerry Lee and Henry,
@Jerry Lee Marcel?I reduced the value of C8 to 1uf. Also there was an error on the C15 value, it should be 1000p instead of 0.1uf.
@William Spragens?The additional RC filter after VR was added to a new PCB design and sent to PCBWay. Thank you!
Here is version 1.1:
Also a quick update, replacing 10V zener with two 5.1V zeners in series, seems to fix the problem with the LF noise, but VCC is reduced from 9.4V to 8.5V aprox. This should not be a problem, since AFAIK...? JFET drain voltage is not critical to get it working in triode mode.
Waiting for the new PCB version with the additional RC filter. Will let you know how it?goes in a?few days.
Kind regards!
HL
An additional RC filter would work, or simply adding a resistor between the BC549 and C14, and increasing C14 to push the RC time constant below audibility. The op-amps have good power supply noise rejection, but the FET has none. It needs pure DC.
The advantage of the zener plus transistor style VR in China mics is operation at low voltage, like 3V PIP for use with PC sound cards. The disadvantage is it's noisy.
|
Phil Manning
Mic Scharf